body {
	/* 背景图片 */
	background: url(../img/bg.jpg) no-repeat center center fixed;
	background-size: cover;
}
.main{
	width: 100vw;
	height: 100vh;
	/* flex容器,水平居中,垂直居中 */
	display: flex;
	justify-content: center;
	align-items: center;
}

.login{
	width: 50vm;
	heigth: 50vh;
	border: 5px solid #FF6600;
	justify-content: center;
	align-items: center;
	border-radius: 10px;
	/* 背景色为白色,半透明 */
	background-color: rgba(255,255,255,0.7);
}